Aw reet, found 'em. (So much easier to find crap on a computer versus rooting through big piles of junk in a rat-infested shed!)
First one is the core tank arrangement for module B. Next shows how it fits inside the module with two flanking rows of angled tanks. That's what the 'bumps' are supposed to represent on the MPC kit. Next shows the bow config, or part of it, it's still a WIP and includes some guesswork. I'm trying to do some cleaner renders of this area for my 3D print collaborator Dave (but am struggling a bit at the moment, sorry, best I have right now).
Last one is the tank cluster for the other fuel module, module A. There are two of these in each module A, not 3 as MPC has it.
I have a few renders showing the insides of the modules without tanks but they do include the spruing I have to use for 3D print. I think with that included they might be a bit confusing.
In short: both modules have a kind of 'wall' of framing at each end, with an airlock in it. They also both have some solid areas of flooring, catwalks of sorts even. So the shelf on the MPC part is probably supposed to represent part of that.